Hybrid electric vehicles use a rechargeable energy storage system to supply electrical power to one or more high-voltage traction motors. The fraction motors alternately draw power from and deliver power to the energy storage system as needed. Motor torque from the traction motors can be used to propel the vehicle in an electric-only operating mode below a threshold vehicle speed. Above the threshold vehicle speed, engine torque from an internal combustion engine is used to propel the vehicle, either alone or in conjunction with motor torque from the traction motors. Vehicle torque security diagnostics or other error detection and analysis procedures are therefore implemented to ensure proper functioning of the vehicle.